oe berlin



Patented Mar. 8, 1932 UNlTED STATES PATENT oFFicE MILTON O. SGHUR AND BENJAMIN G. HOOS, OF BERLIN, NEW ILAMPSHIRE, ASSIGNORS TO BROWN COMPANY, OF BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE PRETREATMENT' F CELLULOSE PRIOR TO NITRATION No Drawing.-

This invention relates to the preparation of nitrocelluloses and has for its object to provide a process of conditioning cellulose fiber to render it more satisfactory for use as a raw material for the preparation of nitrocelluloses such as those employed in the manufacture of films, lacquers, artificial silk, and kindred products.

In U. S. Patent No. 1,701,543, issued February 12, 1929, to George A. Richter, Milton 0. Schur, and Royal H. Rasch, the advantages of treating the fiber with solutions of nitrocellulose in organic solvents prior to nitration are disclosed. It is there stated that the characteristics of the fiber for nitration are markedly improved, as attested by the good quality of the nitrated product and by the higher yield and lower acid retention of the product. A drawback to the commercial application of the process therein disclosed, however, is the fire hazard associated therewithand the high cost of nitrocellulose solvents the loss of which makes the expense of conditioning the fiber excessive.

In accordance with the process of the present invention, the fiber is conditioned for nitration by treating with nitrocellulose dispersed in water, as we have found that beneficial results comparable to those obtained by the use of organic solvent solutions may be procured. Water thus serves as a vehicle or carrier for the nitrocellulose, in lieu of organic solvent, making the conditioning treatment far more economical and greatly reducing the fire hazard. The fiber is preferably dried before nitration, so as to avoid dilution of the nitrating acids.

While not restricted thereto, the process of the present invention may be applied to especial advantage in the case of wood pulp, as such fiber offers good opportunity for improvement. WVhat we have in mind more particularly is a wood pulp of high alpha cel lulose content which may be used as a cotton fiber substitute for the preparation of nitrocelluloses. Such pulp, however, under some circumstances may not be convertible into the nitrate with as high a yield as cotton fiber. By the process of the present invention, however, such fiber may be so modi- Application filed March 19, 1929. Serial No. 348,357.

fied in its characteristics that its yield upon nitration is raised. Apparently, the advantages gained result from the thin coating or film of nitrocellulose produced on the fibers, which, as fully described in the application hereinbefore identified, properly regulates the rate of nitration.

A treatment such as hereinbefore described may be practised advantageously when using pulp of various origins and in beaten, unbeaten, bulk, or sheeted condition. When pulp in bulk condition is treated with an aqueous dispersion of nitrocellulose, precipitation of the nitrocellulose may be effected as by the addition of a suitable precipitating agent, to fix the nitrocellulose on the fibers, whereupon the pulp may be sheeted into paper and the paper then nitrated. Under some conditions, however, it may be more expedient to treat the pulp in the form of Waterleaf paper, and in such case the treatment may be readily carried out continuously and the treated paper then dried continuously, whereupon the dry paper may be nitrated. Nitration may be performed by passing the treated paper in the form of a continuous sheet through a bath of nitrating acid, or the sheet may be shredded or cut into small pieces and nitration effected in pots, as is customarily done.

The amount of nitrocellulose necessary to improve the fiber for nitration is very small, less than 1% aifording a noteworthy gain in yield and lowering of acid retention. The aqueous dispersion of nitrocellulose may be prepared in any suitable manner known to those skilled in the art. For instance, as is known, the aqueous dispersion of nitrocellulose may be produced by initially forming a fairly concentrated solution of low-viscosity nitrocellulose in a suitable organic solvent, such as amyl acetate, and then mixing the solution with a comparatively large amount of water containing a small amount of stabilizer or dispersing agent, such as soap, to keep the dispersed nitrocellulose from precipitating out. A procedure answering this general description appears in British Patent No. 233,367. granted November 6, 1922, to T. lVhittelsey. The aqueous dispersion of nitrocellulose may be applied to pulp in any 7 suitable condition, in some cases it perhaps cellulose content in the form of waterleaf tissue of pounds basis weight was passed.

- through an aqueous dispersion of nitrocellulose, then squeezed free of excess liquid, dried,

and nitrated in the usual way, using a nitrating acid consisting of 20.5% HNO 60.8%

' H 18.7% H O, the ratio of acid to fiber used being 50 to l; The nitration was carried out at 40 C. for 30 minutes. Following are typical results thathave been obtained aca dispersed nitrocellulose distributed there- 'through and fixed thereon but otherwise being in unsized' and unfilled condition.

cording to this procedure, compared with th results from untreated paper: I

Untreated i Treated P P. P 1

. Per cent nitrocellulose in paper 0 l 0. 2 ield I 150. 7 y 154. 5 Initial temperature rise 1. 6 C. y 1. 4 0. Acid retention 3. 6 3. 5 Color of nitrocellulose 21. i 20. Nitrogen content of nitrocellulose 11.00 i 11. 06 Per cent of theoretical yield obtained 97. 4 99.5

From the table hereinbefore given, it is thus seen that the yield of nitrocellulose is notably increased, while the acid retention. is reduced. The product was also slightly better in other characteristics than the product from untreated paper.

An important advantage of the process herein described is that an aqueousmedium serves as the vehicle or carrier-for the nitrocellulose, it thus being possible to treat the fibers uniformly with a thin coating or film oi: nitrocellulose at comparatively low expense.

Having thus described certain embodiments of this invention, it should be evident to those skilled in they art that various changes and modifications might be made therein without departing from the spirit or scope of invention as defined by the append ed claims.

WVe claim:

1. A process which comprises treating cellulose fiber with an aqueous dispersion of nitrocellulose, and then nitrating the fiber.

. 2. A process which comprises treating cellulose fiber with an aqueous dispersion of ggirocellulose, drying, and then nitrating the 3. A process which comprises treating cellulose fiber with an aqueous dispersion of nitrocellulose containing a stabilizer, and then nitrating the fiber.

4;. 1 A process which comprises treating cellulose fiber with a dispersion of nitrocellulose in a water-organic solvent mixture, and then 'nitrating the fiber.

, 5. A process which comprises treating celsignatures.

lulose fiber with a dispersion of nitrocellulose in a water-organic solvent mixture containing a stabilizer, and then nitrating the fiber.

6. A process which comprises treating paper with an aqueous dispersion of nitrocellulose, and then nitrating the paper.

7 A process which comprises treating paper with an aqueous dispersion of nitro cellulose, drying, and then nitrating.

8. A .process which. comprises treating wood pulp with an aqueous dispersion of nitrocellulose, and then nitrating the pulp.

9. A process which comprises treating ,pulpjwith anaqueous dispersion of nitrocelluloses, fixing the nitrocellulose on the fibers, sheeting into paper, and nitrating the aper. v

10. Cellulose fiber containing previously- 13. A waterleat paper of wood fiber of high alphacellulose content containing previously-dispersed nitrocellulose in small amount distributed therethrough and fixed on the fibers.

In testimony whereof we have alfixed our MILTON o. sonun. BENJAMIN o. oos. 

